Insulin-evoked precocious appearance of intestinal sucrase activity in suckling mice.

The effect of insulin (12.5 mU/g body wt/day) on the ontogeny of intestinal sucrase has been studied in suckling mice. Sucrase activity normally appears along the entire small intestine between the 14th and 16th days after birth. The hormonal treatments begin at 8 days and the response of sucrase to one or three injections of hormone is subsequently analyzed in the proximal, middle, and distal intestinal thirds. Three injections of insulin provoke a precocious appearance of sucrase in all intestinal parts, the proximal third exhibiting the highest sucrase activity. Twenty-four hours after a single injection of insulin, sucrase activity can already be detected along the entire small intestine. During the second and third days, the activities observed in the different parts of the small intestine remain stable. These data show that insulin is able to provoke a premature appearance of sucrase activity and appears to play a previously unsuspected role in intestinal maturation.     

Development of the small intestine in the hypophysectomized rat. II. Influence of cortisone, thyroxine, growth hormone, and prolactin.

The intestinal deficiencies caused by hypophysectomy of rats at 6 days of age can be repaired to varying degrees by thyroxine or cortisone but not by growth hormone or prolactin. Administration of daily doses of thyroxine alone from 19–22 days raises duodenal alkaline phosphatase activity to normal levels at 24 days; it has a strong effect on jejunal sucrase and maltase, although these activities remain below those of controls. Thyroxine causes a marked increase in rough endoplasmic reticulum and restores the Golgi complexes to their normal appearance. It also elicits an intensification of periodic acid-Schiff (PAS) stainability of the brush border. Cortisone acetate given from 19 to 22 days elevates sucrase and maltase to normal levels but does not fully restore phosphatase activity. Like thyroxine, cortisone causes intensification of PAS staining of the brush border and also increases rough endoplasmic reticulum. It seems to stimulate Golgi activity, but results in the appearance of a variety of abnormal forms. The defects in Golgi configuration, brush border carbohydrate content, and activity of glycoprotein enzymes that are bound to the brush border may all reflect impaired glycosylation in the hypophyseoprivic state; the results of thyroxine or cortisone administration suggest that both hormones may affect glycosylation but in different ways.     

Cell migration and cortisone induction of sucrase activity in jejunum and ileum

The increase of sucrase activity in homogenates of jejunum and ileum of suckling rats after cortisone administration has been investigated. Serial tissue sections of villi and crypts were also assayed for sucrase activity and these results were compared with the migration of cells labelled with [(3)H]thymidine along the villus. By using a low dose of cortisone (0.5mg/day per 100g body wt.) it was found that the sensitivity of the small intestine producing system to cortisone stimulation increased during the suckling period. On the other hand, 5mg of cortisone/day per 100g body wt. produced practically the same increase of sucrase during the entire suckling period. Sucrase activity in homogenates of the entire small-intestinal wall was first detected 24h after the first injection of cortisone (5mg/day per 100g body weight) to 9-day-old animals and maximum activity both in the jejunum and ileum was reached by 120h. Jejunal activity was greater than ileal activity, but the rate of the increase was similar. The half-time of the increase was 23-27h, whereas enterocytes migrate from the base to the tip of the villi in approximately 72h. Comparison of sucrase activity in serial tissue sections of villi and crypts at various times after cortisone treatment showed that the leading edge of sucrase activity proceeds toward the tip of the villi at the same rate as the advancing edge of newly formed cells. Sucrase activity increased in the newly induced cells as they migrated to the tip of the villi. It was concluded that the increase of sucrase activity in suckling rats after cortisone stimulation is due to at least three factors: (1) increase of activity in newly differentiating cells, (2) increased percentage of villus cells with sucrase activity and (3) continued production or activation of sucrase activity as the cells migrate along the villi.     

小鼠小肠四种消化酶活力的胎后发育模式

为明确晚成型小鼠胎后发育肠道消化酶活力的建立过程和发育模式,探讨其与适应性调节假说的关系,测定了从出生后至27日龄小鼠小肠前、中、后段的乳糖酶、蔗糖酶、麦芽糖酶和氨基肽酶的酶活力。结果发现单位组织酶活力方面,乳糖酶活力先增后降,小肠前段在9日龄而中后段在12日龄达到最高,至27日龄时仅中段有微弱的酶活力;蔗糖酶活力12日龄始出现,前段和后段自15日龄迅速升高,至18日龄达最高,但随后显著降低,而中段在15日龄后持续升高至21日龄达到最高,此后维持在较高水平;麦芽糖酶出生时已具有活力,但在15日龄前维持较低水平,此后迅速升高,前后段在18日龄,中段在21日龄达到峰值,此后下降;小肠前段的氨基肽酶活力出生后至27日龄持续下降,而后段和中段从出生到断乳前则持续升高,断乳后略有下降。除乳糖酶总酶活力先增后降,在15日龄达峰值外,其余3种酶的总酶活力均持续增加。在小肠不同位置4种酶活力的分布具有显著差异,且日龄对不同位置酶活力的影响趋势不同。总之,小鼠小肠4种消化酶的酶活力随时间的变化能够与其食物转变的消化需求相匹配,部分地支持适应性调节假说。     

Development of the small intestine in the hypophysectomized rat. I. Growth histology, and activity of alkaline phosphatase, maltase, and sucrase.

Rats hypophysectomized at 6 days of age continue to grow but at a subnormal rate. At 24 days, when maturation of the intestinal epithelium normally culminates, the intestine is disproportionately small. The crypts are shallow and the mitotic rate low. The villi are short, and they fail to achieve the broad, leaflike form found in controls. The absorptive cells acquire a deep subnuclear zone, and their surfaces apparently cease to carry on pinocytosis. Rough endoplasmic reticulum is however sparse, and the Golgi complexes are small and atypical in structure. Duodenal alkaline phosphatase remains at the low level characteristic of the neonatal intestine. Sucrase activity appears in the jejunum, and maltase activity increases slightly, but both activities are less than a third of those in intact animals at 24 days. If the pituitary is removed later than 6 days, enzyme activities are higher than after early ablation, but they remain deficient even when the operation is performed at 16 days.     

Cortisone and thyroxine modulate intestinal lactase and sucrase mRNA levels and activities in the suckling rat.

Glucocorticoids and thyroxine modulate postnatal intestinal sucrase and lactase activities. Whether changes in enzyme activity are accompanied by changes in enzyme mRNA levels were determined in day 6 rats given thyroxine, cortisone, or thyroxine plus cortisone and killed 3 days later. Cortisone induced precocious expression of jejunal sucrase activity which was enhanced when cortisone plus thyroxine was administered; sucrase mRNA changed in parallel. Jejunal lactase activity was unaffected by thyroxine and was increased after cortisone, but not after thyroxine plus cortisone. Jejunal lactase mRNA levels increased equally after cortisone or after cortisone plus thyroxine. Thus, cortisone induces coordinated increases in sucrase and lactase activities and in corresponding mRNA levels. Thyroxine only enhances cortisone induced sucrase expression and antagonizes cortisone by depressing lactase activity post-translationally.     

Maltase-glucoamylase and trehalase in the rabbit small intestine and kidney brush border membranes during postnatal development, the effects of hydrocortisone

Kidney and intestinal brush border membranes were isolated from 14-day-old rabbits and papa?n solubilized maltase-glucoamylase was purified to almost homogeneity from both membranes. Maltase-glucoamylase from kidney and intestine have the same molecular weight (669,000 daltons by AcA 22 gel filtration) and the same Km (4 mM, for maltose). Tris (Ki = 12.5 mM, for maltose) is a non-competitive inhibitor for both enzymes. In intestine, maltase and glucoamylase have low activity during the first two postnatal weeks and then undergo a sharp increase during the next 2 weeks. In contrast, for trehalase, adult levels are reached about 6 days after birth. Hydrocortisone injection to 10 days rabbits causes precocious increases in the specific activities of trehalase (3.6 x), maltase (5.2 x) and glucoamylase (7.4 x). Conversely, kidney maltase, glucoamylase and trehalase activities rise gradually from birth, reaching adult levels by the end of the third week. Administration of hydrocortisone to suckling rabbit does not affect either trehalase or maltase and glucoamylase in kidney brush border membrane.     

Effects of urogastrone-epidermal growth factor and age at administration on five enzymes in the small intestine of suckling rats.

Suckling rats were given urogastrone-epidermal growth factor (EGF: 1,000 micrograms/kg body weight) or vehicle by gavage at one of three stages of development: 8 to 10, 11 to 13 or 14 to 16 days of age. Intubation was carried out at 8-hourly intervals over these periods. Fourteen to 16 h after the last intubation the rats were killed; that is, at 11, 14 and 17 days respectively. Samples of proximal and distal small intestine (SI) were taken for enzyme analysis. Five enzymes were assayed; sucrase, lactase, gamma-glutamyl transferase, alkaline phosphatase and neutral amino-peptidase, and their activities expressed per g protein. Treatment with EGF had no effect on body weight or on the length of the small intestine at any age. The nature of the effects on enzyme activities depended on the specific enzyme concerned, the site within the small intestine and the timing of the treatment. Lactase was increased by EGF at both sites only on day 14, whereas gamma-glutamyl transferase was increased in proximal samples at 11 and 14 days, and in distal samples at 17 days. Nor was the outcome always to increase activity. On day 11 alkaline phosphatase was increased in proximal SI, but decreased in distal SI; and so too was aminopeptidase N decreased in distal SI at 11 days. Sucrase showed no response at all. The pattern is complex. Certainly it does not indicate accelerated functional maturation.     

Development of sucrase in the chick small intestine

Development of sucrase in the chick small intestine was studied biochemically and immunologically using antiserum prepared against purified chick intestinal sucrase. Sucrase activity was first detectable at 10 days of incubation and increased with age. After a transient drop at 20 days, the activity rapidly increased to the adult level. Immunodiffusion and polyacrylamide gel electrophoretic studies suggested that the sucrase of the embryonic and hatched chick intestines was identical except for a difference in the content of sialic acids. In immunofluorescence and immunoelectron microscopy, sucrase was found to appear on the luminal surface of epithelial cells at 8-10 days of incubation, soon after the start of morphological differentiation from an undifferentiated thick epithelium to a thin simple epithelium.     

Autonomous biochemical and morphological differentiation in fetal rat intestine transplanted at 17 and 20 days of gestation

The morphological and biochemical development of fetal rat intestine was examined for up to 5 weeks following transplantation to syngeneic hosts at 17 and 20 days of gestation. In transplants of both ages, normal villi bearing mature enterocytes developed. In addition, the disaccharidases lactase, maltase, and sucrase, as well as alkaline phosphatase, underwent normal patterns of development. Lactase activity, initially high, fell significantly, while maltase and sucrase activities increased significantly in the interval between 2 and 5 weeks following transplantation. During this same period, alkaline phosphatase developed the proximally located, high-activity form. The transplanted intestine also developed normal topographical distributions of enzyme activities. Measurement of corticosterone levels demonstrated that, except for a transient upsurge at the time of operation, hormone levels did not change significantly during the period of transplant maturation. These data indicate that the brush-border enzymes of the small intestine develop according to an intrinsic program which is already established as early as 17 days of gestation.     

Influence of duodenal secretions and its components on release and activities of human brush-border enzymes

The in vitro effects of human duodenal secretions and various combinations of its components on activity and release of enzymes from the human brush border were examined. Sucrase retained activity for 90 min in duodenal secretions, and maltase was almost as stable; lactase lost activity rapidly and alkaline phosphatase was of intermediate stability. Inactivation of lactase could only be partly (50%) attributed to luminal proteases, bile salts and phospholipids played no role. Rate of release of an enzyme from the brush border bore no relationship to its rate of inactivation. When individual proteases were studied, elastase was the most potent for releasing disaccharidases from the brush border; trypsin was ineffective alone but augmented the effect of elastase. Sucrase and maltase were activated by proteolytic release, but activation was abolished by simultaneous exposure of brush borders to bile salts. Lactase was released and rapidly inactivated by proteinases, while alkaline phosphatase appeared to be inactivated without significant release. These results show that there are significant interactions between luminal factors which have been inapparent when studying them in isolation. Loss of functionally useful enzyme does not follow release of sucrase or maltase from the brush border into the lumen but does follow release of lactase. Study of the susceptibility of lactase to inactivation by luminal factors in the various forms of lactose intolerance is warranted.     

Ontogenesis of intestine morphology and intestinal disaccharidases in chickens (Gallus gallus) fed contrasting purified diets

Two groups of growing posthatching Cornish x Rock cross chickens were fed with either a carbohydrate-containing (52.5%) or a carbohydrate-free diet. At 36 days after hatching some of the chicks in each group were shifted to the opposite diet. Chickens fed on a carbohydrate-containing diet grew faster and achieved higher asymptotic masses than chickens fed on a carbohydrate-free diet. Chickens fed on a carbohydrate-free diet had longer intestines and larger intestinal areas than chickens of the same mass fed on a carbohydrate-containing diet. In both groups sucrase and maltase activity (standardized by either intestinal area or mass) increased from day 1 to approximately day 17. After day 17, chickens fed on a carbohydrate-containing diet exhibited 1.8 and 1.9 times higher sucrase and maltase activities per unit intestinal area, respectively, than chickens fed on a carbohydrate-free diet. Analysis of covariance was used to estimate the contribution of sucrase and the sucrase-independent maltases to maltase activity, and to estimate the effect of diet on the sucrase-independent maltases. Sucrase contributed 80% and 75% of the maltase activity in carbohydrate and carbohydrate-free fed chickens, respectively. Chickens shifted from a carbohydrate-free to a carbohydrate diet converged in gross intestinal morphology and intestinal sucrase and maltase levels with carbohydrate-fed chickens within 8 days. Chickens shifted from carbohydrate to carbohydrate-free diets, in contrast, did not show appreciable changes in intestinal length and after 8 days had not reduced levels of sucrase and maltase to those of chickens fed on the carbohydrate-free diet. A comparison of integrated maltase intestinal activity with published data on glucose uptake showed that the ratio of maltose hydrolysis to glucose uptake seemed to be about 7 and to remain relatively invariant during ontogeny. Because so little is known about the interaction between hydrolysis and uptake in vivo, it is difficult to determine if this relatively high ratio represents excess hydrolytic capacity or if it is needed to provide high lumenal glucose concentrations that maximize uptake.Abbreviations m body mass - K _m Michaelis constant - K _m ^* apparent Michaelis constant - GI gastro-intestinal     

Effects of hypoxia on the development of intestinal enzymes in neonatal and juvenile rats

Hypoxia in the neonate is known to alter the activity of hepatic and pancreatic enzymes involved in lipid and carbohydrate metabolism. The purpose of this study was to evaluate the effect of neonatal hypoxia on the activity of intestinal enzymes, and to determine whether the administration of glucocorticoids to neonates can mimic the effects of hypoxia. Hypoxia in neonatal rats (0-7 days) increased protein content, and lactase and maltase activity in the duodenal and the jejunal segments of the small intestine compared with normoxic controls. Hypoxia in juvenile rats (28-35 days) did not change these enzymes. Two weeks after returning hypoxic (0-7 days) pups to normoxia, their body weight remained lower than the age-matched controls. In the group recovering from hypoxia, sucrase, maltase, and leucine aminopeptidase activities were lower in the duodenal and the jejunal segment. Compared with controls, LDH activity was lower only in the jejunal intestine in the group recovering from hypoxia. All enzyme activities returned to control levels 3 weeks after recovery. Neonatal rats treated with dexamethasone had a decrease in body weight, but increases in sucrase and maltase activity in both the duodenal and the jejunal segment. Hypoxia in newborn rats caused a delayed maturation of small intestinal enzymes. Increases in serum glucocorticoids after hypoxic exposure probably do not play a major role in the delayed maturation of the disaccharidase activity in the small intestine.     

Circadian rhythms in disaccharidases of rat small intestine and its relation to food intake.

The activities of maltase and sucrase of the small intestine were low at night and high in the daytime in rats which had been fed from 09.00 h to 15.00 h for 2 weeks. A remarkable rise of enzyme activities was observed at 08.00 h, 1 h before the start of feeding. The rhythmic changes in disaccharidase activities continued for at least 2 days after starvation, but completely disappeared after 5 days of starvation. It was suggested that the disaccharidase rhythms are not a direct consequence of food intake, but that anticipation of food intake acts as a trigger for initiation of the disaccharidase rhythms.     

Action of actinomycin D on glycosidase levels in the small intestine of hamsters

Actinomycin D affects a number of functions of the epithelial cells of the small intestine. Maltase, saccharase and lactase levels in the small intestine of hamsters treated with various dosages of actinomycin D over various periods of time, differed from those observed in control animals: administration of 0.25 micrograms/g body weight, gave rise to a statistically significant increase in the maltase and saccharase levels measured after 4 h and a statistically significant reduction in the lactase levels measured after 8 h; administration of 1.5 micrograms/g body weight reduced the activity of all three enzymes at all times post-administration, the decrease being statistically significant for maltase after 2 and 8 h.     

Inhibition of beta-fructofuranosidases and alpha-glucosidases by synthetic thio-fructofuranoside

A synthetic beta-thio-fructofuranoside of mercaptoethanol inhibited not only beta-fructofuranosidases but also alpha-glucosidases. The compound was hardly hydrolyzed by the glycosidases. The thio-fructoside competitively inhibited beta-fructofuranosidases from Aspergillus niger, Candida sp., and Saccharomyces cerevisiae, but not Arthrobacter beta-fructofuranosidase at all. Sucrase activity of rat intestinal sucrase/isomaltase complex was also suppressed in the presence of the thio-fructoside. The thio-fructoside showed noncompetitive inhibition toward maltase activity of the rat intestinal enzyme complex and Saccharomyces sp. alpha-glucosidase. Inhibition against the Bacillus stearothermophilus alpha-glucosidase, Rhizopus glucoamylase, and porcine kidney trehalase were more slight than that against these two alpha-glucosidases.     

Activity of renal hydrolases in pre- and postnatal development of mice

The fetal and postnatal activity patterns of different hydrolytic enzymes (alkaline phosphatase, gamma-glutamyltransferase, trehalase, maltase, glucoamylase, lactase, and sucrase) have been examined in mouse renal homogenates. Alkaline phosphatase and gamma-glutamyltransferase activities presented approximately similar changes. They increased from 18 days of gestation up to 30 days after birth. These activities showed marked increases during the 3rd and 4th postnatal weeks. A similar important rise was observed for trehalase activity at the end of the suckling period. Maltase activity increased gradually after birth. Traces of lactase, sucrase, and glucoamylase activities were detected at each developmental stage.     

Carbohydrase activities in the bovine digestive tract

1. The carbohydrase activities of homogenates of mucosa from the abomasum, small intestine, caecum and colon, and of the pancreas of cattle were studied. 2. The disaccharidase activities were located mainly in the small intestine and showed a non-uniform pattern of distribution along the small intestine; trehalase activity was highest in the proximal part, lactase and cellobiase activities were highest in the proximal and middle parts and maltase activity was highest in the distal part. 3. The intestinal lactase and cellobiase activities were highest in the young calf and decreased with age, whereas the intestinal maltase and trehalase activities, which were very low compared with the lactase activity, did not change with age. 4. No intestinal sucrase or palatinase activity was detected in the calf or in the adult cow. 5. Homogenates of intestinal mucosa also exhibited amylase and dextranase activity. 6. Homogenates of the pancreas possessed a strong amylase activity and a weak maltase activity. The maltase activity did not change with age, whereas the amylase activity increased with age. 7. No marked differences were observed between the carbohydrase activities of calves fed solely on milk and those of calves given a concentrate-hay diet from 6 weeks of age.     

The effect of dexamethasone on the development of rat intestinal brush border enzymes in organ culture

The effect of dexamethasone on the evolution pattern of brush border enzymes was examined in the rat jejunum cultured in vitro at different postnatal stages (4 to 21 days). Enzymic activities were analyzed in purified brush border membranes isolated from noncultured intestine and from explants cultured for 24 and 48 hr. The data obtained from this study indicated that dexamethasone exhibits two types of effects on the cultured intestinal tissue: (1) a nonspecific but protective effect against the drastic drop of all enzyme activities as well as against a loss of villus cells observed in control cultures, and (2) a direct and specific effect on precocious induction of sucrase and on stimulation of maltase activity. The SDS-polyacrylamide gel patterns of brush border membrane proteins showed that in the 6-day-old intestine, appearance of sucrase as well as stimulation of maltase activities elicited by dexamethasone were accompanied by a simultaneous appearance or enhancement of the corresponding protein bands. Furthermore, the radioactivity peaks on gels due to the incorporation of ¹⁴C-valine and of ¹⁴C-fucose indicated that dexamethasone induces the synthesis of new proteins or at least the glycosylation of preexisting proteins which may lead to the formation of active maltase and sucrase molecules.     

Formation of Phage-Induced γ-Polyglutamic Acid Depolymerase in Lysogenic Strain of Bacillus natto

The influence of tea catechins on the absorption of starch or sucrose was investigated in vivo. Tea catechins were administered orally to rats before soluble starch or sucrose administration. Saccharide-dosed rats were killed and the blood and the contents of the intestine were collected at intervals over two hours. Catechins of certain concentrations suppressed the increase of plasma glucose levels, thus concurrently suppressing insulin activity. Increased activity of intestinal α-amylase by starch dosing was inhibited markedly in the catechin-administered rats. Sucrase on the brush border membrane was also inhibited by prior catechin administration. From these results it was assumed that orally administered catechins will inhibit intestinal α-amylase or sucrase, thereby deterring the digestion of certain amounts of starch or sucrose and eventually reducing the plasma glucose levels.